BUCKLING MODES OF SCREWED CONNECTIONS IN COLD-FORMED STEEL BUILT-UP PLATES

Discrete screws can introduce discontinuities at the interface of built-up plates, leading to various buckling modes in cold-formed steel (CFS) built-up plates, namely coordinated buckling and delamination buckling. The impact of these buckling deformation modes on the stability mechanism of CFS screw-connected built-up plates is significant and cannot be overlooked. Consequently, this paper establishes theoretical models for both buckling modes. Analytical solutions for the critical buckling stress (CBS) of the screw-connected built-up plate under these two modes are derived. The validity of the buckling modes and the analytical solutions is confirmed through experimental verification. The results indicate that: (1) delamination buckling is invariably a higher-order mode in comparison to coordinated buckling, and as such, only coordinated buckling is required for calculating the CBS; (2) the CBS calculation method proposed in this paper aligns more closely with the actual mechanical behavior of screw connections in CFS built-up plates.